Referring first to FIG. 1, a known conventional bending apparatus is shown. In the figure reference numeral 1 designates a steel pipe to be bent; a support block 2 is adapted to support the pipe end and formed integral with the means for continuously and straightforwardly propelling the steel pipe 1. Also provided are a pair of guide rolls 3 and 4 and a heating device 5 such as an annular high frequency inductor which is capable of heating a limited area of the steel pipe 1 sidewise to a high temperature, a cooling device 6 integral with said heating device, a bending arm 7, the pivotal shaft 8 of the arm 7 arranged such that its center resides within the plane of the heating device 5, and a clamp 9 fixed to the arm 7.
In operation of the apparatus just described, steel pipe 1 is first passed between guide rolls 3 and 4 and then further passed through heating device 5 as shown in the drawing. The pipe end is supported by support block 2 of the propelling means, and in certain applications, an end or a suitable middle portion of the steel pipe 1 is fastened to the arm 7 by the clamp 9. The steel pipe 1 is continuously fed straightforwardly by the propelling means while subjected to local heating by heating device 5 to a plastic deformation inducing temperature, and this treatment is immediately followed by cooling so as to effect continuous plastic deformation of the steel pipe 1 in its heated area while giving a bending movement to the pipe by the thrust of the propelling means under the guidance of the arm 7, thereby to accomplish the desired bending. Thus, according to this apparatus, the desired bending of steel pipe can be performed at high efficiency without requiring any elaborate thermal works. The same effect can be obtained by using this apparatus for bending of other types of metal pipes or metal strips. It is to be particularly noted that no bending mold is required and it is possible to bend the pipe at any desired radius of curvature.
The above-described means and method has the disadvantages that it requires numerous rollers and a bending arm fixed to a strong frame in order to resist undesired movement when a bending moment is applied to the elongated material. As a result the apparatus is expensive to fabricate and difficult to make portable to permit on-site bending of materials.
Accordingly, it is an object of the present invention to provide a bending means which may be inexpensively fabricated.
It is another object of the present invention to provide a portable hot bender for elongated materials.
A demand has been voiced in the industry for a method and apparatus which is capable of bending elongated material with high precision.
Accordingly, it is still another object of the present invention to provide a high precision bending apparatus.
These and other objects and features of the invention will become apparent from the claims and from the following description when read in conjunction with the appended drawings.